Wireless networks, known as WLANs (Wireless Local Area Networks), are increasingly being installed in small, local areas known as “hot spots” such as, for example, airports, hotels or similar areas with a high subscriber density. Because of the technical possibilities afforded by WLAN it is desirable to use this technology as an add-on to mobile radio systems of the third generation such as, for example, UMTS (Universal Mobile Telecommunications System).
FIG. 1 shows the basic principle of a WLAN network architecture in a schematic representation. It depicts a wireless local communication network in which mobile stations MTs (Mobile Terminals) are connected by radio via a number of access nodes APs (Access Points) to a broadband data network (BDN). The access nodes APs are WLAN base stations. Each access node AP supplies all the mobile terminals MTs contained in a cell. In this case, the cell size may extend to a maximum of several hundred meters. In principle, WLANs can be used to build a cellular radio network in which an existing data connection can be handed on from access node to access node in line with the movement of the mobile terminals MT. In mobile radio contexts this is generally known as “roaming”. The maximum data rates are dependent on the respective WLAN technology and can range up to 54 Mbit/s.
To connect a WLAN in UMTS, an architecture is known in which WLAN and UMTS represent autonomous systems that are connected to each other via an interworking unit (IWU). FIG. 2 shows this known network architecture in a schematic representation. The purpose of the element IWU is to convert signaling and user data from WLAN to UMTS and vice versa. The WLAN is represented with the elements AP, router and AAAL. The APs are, in turn, access nodes, the router is a switching processor and the AAAL (Authentication Authorization Accounting Local) is a local computer which is used for authentication, authorization and accounting. The network architecture of UMTS is shown with the elements NodeB, RNC, SGSN, GGSN and HSS. NodeB is a UMTS base station, the RNC (Radio Network Controller) is a radio network control element, SGSN (Serving GPRS Support Node) and GGSN (Gateway GPRS Support Node) are GPRS support nodes and the HSS (Home Subscriber Server) is a local subscriber computer. GPRS (General Packet Radio Service) is a mobile radio standard according to which a dedicated data connection is not set up for each subscriber, but instead the total number of available transmission resources is allocated as needed to the individual subscribers, and the data is transmitted in packets.
In the UMTS, the actual terminal station, designated in the diagram as user facility UE (User Equipment), consists of the mobile facility ME (Mobile Equipment) and the physical chip card UICC (Universal Integrated Circuit Card). FIG. 3 shows the corresponding layout of user equipment UE in schematic form. The USIM (Universal Subscriber Identity Module) together with the USAT functionality (USIM Application Toolkit) is implemented as standard on the UICC. The USIM corresponds to the SIM (Subscriber Identity Module) in the second-generation mobile radio standard GSM (Global System for Mobile Communications). The USIM enables a mobile radio subscriber to use his or her ME in a UMTS radio network. All the important data of the subscriber access is stored on the USIM, such data serving to identify and to prove the access authorization, that is to say authentication, of the mobile radio subscriber, as well as to ensure encryption and decryption of the user data as protection against eavesdropping and tampering or corruption. The USAT functionality enables the ME to be configured directly via the UMTS radio network. Technical specification TS 31. 111 Version 4. 5. 0 (2001-12) “USIM Application Toolkit (USAT)” of the 3rd Generation Partnership Project (3GPP) deals with the interface between the ME and the UICC and essentially includes a list of commands which the ME can convert interactively with the UICC.
With the desired connection of WLAN in UMTS there is, however, the problem that frequent connection setups and/or cleardowns are necessary due to the non-permanent availability of the WLAN. Known procedures are handicapped by high signaling overhead or often cannot guarantee reliable connection setup and/or cleardown. Furthermore, because of the USIM/USAT standardization in UMTS, an existing data connection in the WLAN should be monitored by the USIM/USAT of the UMTS terminal station. However, an implementation of a corresponding process of control is not known to date.
The present invention is, therefore, directed toward a method and a data system for connecting a wireless local network to a UMTS terminal station with USIM/USAT functionality which enables an exchange of WLAN-specific data between a UMTS terminal station and UICC and, in addition, guarantees reliable connection setup and/or cleardown.